Variable Not Defined Compiler Error

Question

I am a long time avid Excel user but am just starting to learn VBA. I am using the following code but am getting an error when I try to run Sub test:

Compile Error:Variable not defined

Can you help me figure out what is wrong?

Option Explicit

Function toFarenheit(degrees)
    toFarenheit = (9 / 5) * degrees + 32
End Function

Function toCentigrade(degrees)
    toCentigrade = (5 / 9) * degrees - 32
End Function

Sub test()
    answer = toCentigrade(55)
    MsgBox answer    
End Sub

Answer 1

You have Option Explicit turn on which means you must declare your variables before using them.

In Sub test, you are missing a declaration for answer. Adding this should fix it:

Sub test()
    Dim answer As Variant
    answer = toCentigrade(55)
    MsgBox answer    
End Sub

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Edit

Since you are new to VBA, you might want to consider typing both your variables and function returns. You don't have to do this (and everything will be treated as a Variant), but it is good practice.

If you type everything properly, your example would become:

Option Explicit

' Accept a double value and return a double type value.
Function toFarenheit(degrees As Double) As Double
    toFarenheit = (9 / 5) * degrees + 32
End Function

Function toCentigrade(degrees As Double) As Double
    toCentigrade = (5 / 9) * degrees - 32
End Function

Sub test()
    ' Variable type matches what the function will return.
    Dim answer As Double
    answer = toCentigrade(55)
    MsgBox answer    
End Sub